EN 1993-4-1:2026/prA1

• Abstract:

  1.1 Scope of EN 1993 4 1; (1) prEN 1993 4 1 provides rules for the structural design of steel silos of circular or rectangular plan-form, being free-standing (on ground) or supported on a structural framework (elevated).; (2) prEN 1993 4 1 is applicable to silos constructed from isotropic rolled plates that are stiffened or unstiffened, from corrugated sheeting that is stiffened or unstiffened and from flat or corrugated plates assembled into box structures of different geometries. It applies to vertical walls, hoppers, roof structures, transition junctions and support structures.; (3) prEN 1993 4 1 does not apply to storage vessels for silage and haylage, or to the storage of materials that are not free-flowing (see EN 1991 4). This Part 4-1 also does not cover:; - resistance to fire;; - cylindrical silos with internal subdivisions;; - internal structures within a single silo (except for internal ties, as defined in 12.5);; - silos with capacity less than 100 kN (10 tonnes);; - hoppers that are supported on a structural framework;; - cases where special measures are necessary to limit the consequences of accidents.; (4) This document is applicable to silos within the following dimensional limits (see EN 1991-4):; - Silo aspect ratio hb/dc < 10 ; - Silo total height hb < 70 m ; - Silo equivalent diameter dc < 60 m ; NOTE These dimensional limitations are more limited than those of EN 1991-4 which also applies to silos constructed from other materials.; (5) Where this standard applies to circular planform silos, the geometric form is restricted to axisymmetric structures, but unsymmetrical actions on them and supports that induce forces in the silo structure that are not axisymmetric are included.; (6) This part is concerned only with the requirements for resistance and stability of steel silos. For other requirements (such as operational safety, functional performance, fabrication and erection, quality control, details like man-holes, flanges, filling devices, outlet gates and feeders, etc.), see other relevant standards and information.; (7) This part is concerned with both isolated silo structures and silos that are connected to others to form a battery of silos, but throughout this document the term silo refers to a single cell within a battery.; (8) Provisions relating to special requirements of seismic design are provided in EN 1998 4, which complements or adapts the provisions of Eurocode 3 specifically for this purpose.; (9) The structural design of supporting structures for the silo are dealt with in EN 1993 1 1. The supporting structure is deemed to consist of all structural elements beneath the bottom flange of the lowest ring of the silo (see Figure 1.1), though information on some forms of support structure is given in Clause 8 of this document.; (10) Foundations in reinforced concrete for steel silos are dealt with in EN 1992 (all parts) and EN 1997 (all parts).; 1.2 Assumptions; (1) Unless specifically stated, the provisions of EN 1990, EN 1991 (all parts) and EN 1993 1 (all parts) apply.; (2) The design methods given in EN 1993 4 1 are applicable if:; - the execution quality is as specified in EN 1090 2, and; - the construction materials and products used are as specified in the relevant parts of EN 1993 (all parts), or in the relevant material and product specifications.; Figure 1.1 - Terminology used in silo structures; ...

• Status: Not Published
• Publication Date: 24-Aug-2027
• ICS: 65.040.20 - Buildings and installations for processing and storage of agricultural produce
• ICS: 91.010.30 - Technical aspects
• ICS: 91.080.13 - Steel structures
• Technical Committee: CEN/TC 250 - Structural Eurocodes
• Drafting Committee: CEN/TC 250/SC 3/WG 15 - Evolution of EN 1993-4-1 - Silos
• Current Stage: 4020 - Submission to enquiry - Enquiry
• Start Date: 17-Sep-2026
• Due Date: 29-Sep-2026
• Completion Date: 17-Sep-2026
• Ref Project: SIST EN 1993-4-1:2026/oprA1:2026 - Eurocode 3 - Design of steel structures - Part 4-1: Silos

• Amends: EN 1993-4-1:2026 - Eurocode 3 - Design of steel structures - Part 4-1: Silos
• Effective Date: 10-Jun-2026

EN 1993-4-1:2026/prA1 is a CEN draft amendment to Eurocode 3, Part 4-1, for the structural design of steel silos. It updates the rules for silos of circular or rectangular plan-form, including free-standing and elevated silos, and it focuses on resistance and stability. For engineers, it matters because it refines the classification, stiffness checks, support-condition checks and terminology used when designing silo walls, hoppers, transition junctions and base rings.

What does EN 1993-4-1:2026/prA1 specify?

EN 1993-4-1:2026/prA1 amends the Eurocode rules for the design of steel silos. The underlying part applies to silos made from isotropic rolled plates, corrugated sheeting, and flat or corrugated plates assembled into box structures, and it covers vertical walls, hoppers, roof structures, transition junctions and support structures.

The scope excludes silage and haylage storage, non-free-flowing materials, fire resistance, cylindrical silos with internal subdivisions, most internal structures within a silo, very small silos, hoppers supported on a structural framework, and special accident-limiting measures. The document is organized around changes to the Introduction, Clause 3, Clause 4, Clause 7, Clause 8, Clause 10, Clause 12, Annex A and Annex C.

Annex	What it covers
Annex A	Simplified rules for isotropic walled circular silos in Silo Group 1
Annex C	Formulae for membrane stress resultants in conical hoppers

What are the key requirements of EN 1993-4-1:2026/prA1?

• Clause 4.3.2 and Table 4.1 clarify how to choose the Structural Complexity Class using parameter w. The amendment also distinguishes elevated discretely-supported silos, large silos designed with a Silo Special Load Case from EN 1991-4, silos with w > 20 m, and double-walled or other non-conventional silo types. In practice, this affects which level of design treatment and checking applies.

• Clause 7.5.2 revises the check for the top ring of open silos so it has enough elastic stiffness to provide the right boundary condition for buckling of the stepped wall shell. The clause also states when to use LBA or GNA instead of the simplified stiffness method. That matters when you are proving buckling resistance at the upper edge.

• Clause 8.10 updates support-condition checks for cylindrical walls. The new text links the assessment to revised geometric and stiffness criteria, so designers must re-check the support arrangement rather than relying on older wording. This is important for elevated or discretely supported silos.

• Clause 10.2.2 and 10.3.2.3 revise the treatment of transition junctions and base rings in circular silos, including figures and notational corrections. In practice, this affects detailing and the way junction geometry is interpreted in design calculations.

• Clause 12.5 updates the ultimate limit state design of rectangular and polygonal silos, including internal ties and the use of a hollow section. This matters for box-type silos where tie forces and member selection have to be checked explicitly.

• Annex A keeps the simplified rules for isotropic walled circular silos in Silo Group 1, with notation corrected from lower-case to upper-case L. Annex C revises the hopper coordinate definition so the origin is at the apex, which keeps membrane stress resultants consistent in conical hopper calculations.

What terms does EN 1993-4-1:2026/prA1 define?

• Structural Complexity Class - the classification used in Clause 4 to set the design approach for a silo.
• Silo Special Load Case - a load case from EN 1991-4 used when classifying certain silos.
• LBA - linear buckling analysis, used to check whether the top ring is adequate for buckling resistance.
• GNA - geometrically nonlinear analysis, used where the simplified top-ring method is not suitable.
• Silo Group 1 - the circular silo group covered by the simplified rules in Annex A.
• Internal ties - the internal structural elements within a silo that the scope specifically allows.
• Top ring - the upper ring that provides boundary stiffness for the shell at the silo head.
• Hollow section - the member type named in Clause 12.5.4 for rectangular and polygonal silo ties.

Who uses EN 1993-4-1:2026/prA1?

EN 1993-4-1:2026/prA1 is used by structural engineers, silo designers, checking engineers, and reviewers working on steel silos for storage and processing installations. It is also relevant to buyers, plant owners and quality managers who need to confirm that silo design, support structure design, execution quality and related checks are aligned with the Eurocode system.

What changed in EN 1993-4-1:2026/prA1 from the previous edition?

EN 1993-4-1:2026/prA1 amends EN 1993-4-1:2026. The main changes stated in the document are clarifications to Structural Complexity Class selection using parameter w, a corrected method for determining the required top ring stiffness for open silos under external pressure, internal vacuum and wind, and wording and typing corrections throughout the document.

Which standards are used with EN 1993-4-1:2026/prA1?

• EN 1990-1 - basis of structural and geotechnical design for new structures.
• EN 1991-4 - actions on silos, including the Silo Special Load Case.
• EN 1993-1-1 - general rules for steel structures, including supporting structures.
• EN 1993-1-8 - design of connections.
• EN 1993-1-9 - fatigue design.
• EN 1998-4 - seismic design provisions for silos.
• EN 1992 (all parts) - reinforced concrete foundations.
• EN 1997 (all parts) - geotechnical design of foundations.
• EN 1090-2 - execution quality for steel structures.
• EN 1993 (all parts) - material and product rules used where relevant.

What does the EN 1993-4-1:2026/prA1 document contain?

The document contains amended text, tables, formulas and figures rather than a full rewrite of the Eurocode part. It updates Table 4.1 and related design-class wording, revises the top-ring stiffness method in Clause 7, changes support-condition checks in Clause 8, and corrects figures in Clause 10.

It also updates formulas in Clause 12 for rectangular and polygonal silos, revises notation in Annex A, and clarifies the hopper coordinate system in Annex C. These changes are used for design calculations, stability checks, detailing decisions and review of silo structures.

SLOVENSKI STANDARD
01-november-2026
Evrokod 3 - Projektiranje jeklenih konstrukcij - 4-1. del: Silosi
Eurocode 3 - Design of steel structures - Part 4-1: Silos
Eurocode 3 - Bemessung und Konstruktion von Stahlbauten - Teil 4-1: Silos
Eurocode 3 - Calcul des structures en acier - Partie 4-1: Silos
Ta slovenski standard je istoveten z: EN 1993-4-1:2026/prA1
ICS:
65.040.20 Poslopja in naprave za Buildings and installations for
predelavo in skladiščenje processing and storage of
kmetijskih pridelkov agricultural produce
91.010.30 Tehnični vidiki Technical aspects
91.080.13 Jeklene konstrukcije Steel structures
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
EN 1993-4-1:2026
NORME EUROPÉENNE
EUROPÄISCHE NORM
prA1
September 2026
ICS 65.040.20; 91.010.30; 91.080.13
English Version
Eurocode 3 - Design of steel structures - Part 4-1: Silos
Eurocode 3 - Calcul des structures en acier - Partie 4-1: Eurocode 3 - Bemessung und Konstruktion von
Silos Stahlbauten - Teil 4-1: Silos
This draft amendment is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee CEN/TC 250.

This draft amendment A1, if approved, will modify the European Standard EN 1993-4-1:2026. If this draft becomes an
amendment, CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for
inclusion of this amendment into the relevant national standard without any alteration.

This draft amendment was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 1993-4-1:2026/prA1:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Modifications to the Introduction . 4
2 Modifications to Clause 3, "Terms, definitions, symbols, sign conventions and units" . 4
3 Modifications to Clause 4, “Basis of design” . 4
4 Modifications to Clause 7, “Ultimate limit state design of cylindrical shell walls” . 5
5 Modifications to Clause 8, “Support conditions for cylindrical walls” . 6
6 Modifications to Clause 10, “Ultimate limit state design of transition junctions and base
rings in circular silos” . 6
7 Modifications to Clause 12, “Ultimate limit state design of rectangular and polygonal
silos” . 7
8 Modification to Annex A, “Simplified rules for isotropic walled circular silos in Silo Group
1” . 7
9 Modification to Annex C, “Formulae for membrane stress resultants in conical hoppers” . 7

European foreword
This document (EN 1993-4-1:2026/prA1:2026) has been prepared by Technical Committee CEN/TC 250
“Structural Eurocodes”, the secretariat of which is held by BSI. CEN/TC 250 is responsible for all
Structural Eurocodes and has been assigned responsibility for structural and geotechnical design matters
by CEN.
This document is currently submitted to the CEN Enquiry.
This document will amend EN 1993-4-1:2026.
NOTE Some modifications are purely editorial corrections to improve the quality of the document and these
will not be tagged in the consolidated publication, as noted after the modification.
The following main changes to EN 1993-4-1:2026 are included in the amendment:
— clarifications on the choice of the Structural Complexity Class depending on the parameter w
(Table 4.1),
— correction of the method to determine the necessary top ring stiffness for an open silo to resist
buckling under external pressure, internal vacuum and wind (subclause 7.5.2),
— correction of several wordings and typing errors throughout the document.
The first generation of EN Eurocodes was published between 2002 and 2007. This document forms part
of the second generation of the Eurocodes, which have been prepared under Mandate M/515 issued to
CEN by the European Commission and the European Free Trade Association.
The Eurocodes have been drafted to be used in conjunction with relevant execution, material, product
and test standards, and to identify requirements for execution, materials, products and testing that are
relied upon by the Eurocodes.
The Eurocodes recognize the responsibility of each Member State and have safeguarded their right to
determine values related to regulatory safety matters at national level through the use of National
Annexes.
1 Modifications to the Introduction
In 0.1 replace “— New parts are under development, e.g. EN 19101 Eurocode 11 for design of fibre-
polymer composite structures and EN 19102 Eurocode 12 for
...